feat: add structured backend logging

Collector failures, service-API errors, WS connection lifecycle, and
config reload/discovery events were previously invisible outside the
browser (or, for a few config/discovery cases, logged with an
inconsistent ad-hoc console.error). Add a small scoped logger
(lib/logger.ts, level via LOG_LEVEL) and wire it through server.ts,
the scheduler, service collector, config loader/effective store, and
the WS server so operators can see failures via `docker logs`.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/config/loader.ts

@@ -5,11 +5,18 @@ import chokidar, { type FSWatcher } from "chokidar";
 import { parse as parseYaml } from "yaml";
 import { configSchema, type Config } from "./schema";
 import { interpolateEnv } from "./interpolate";
+import { createLogger } from "@/lib/logger";
+
+const log = createLogger("config");
 
 const CONFIG_DIR = path.join(process.cwd(), "config");
 const CONFIG_PATH = path.join(CONFIG_DIR, "config.yml");
 const ENV_PATH = path.join(CONFIG_DIR, ".env");
 
+function widgetCount(config: Config): number {
+  return config.groups.reduce((sum, group) => sum + group.widgets.length, 0);
+}
+
 export class ConfigError extends Error {}
 
 function loadEnv(): Record<string, string | undefined> {
@@ -62,6 +69,7 @@ class ConfigStore {
 
   load(): Config {
     this.current = readConfig();
+    log.info("config loaded", { groups: this.current.groups.length, widgets: widgetCount(this.current) });
     return this.current;
   }
 
@@ -85,7 +93,11 @@ class ConfigStore {
       awaitWriteFinish: { stabilityThreshold: 200, pollInterval: 50 },
       ignoreInitial: true,
     });
-    this.watcher.on("all", () => this.reload());
+    this.watcher.on("all", (event) => {
+      log.debug("watched file changed", { event });
+      this.reload();
+    });
+    log.info("watching config files", { paths: [CONFIG_PATH, ENV_PATH] });
   }
 
   stop(): void {
@@ -97,10 +109,11 @@ class ConfigStore {
     try {
       const next = readConfig();
       this.current = next;
+      log.info("config reloaded", { groups: next.groups.length, widgets: widgetCount(next) });
       for (const listener of this.listeners) listener(next);
     } catch (err) {
       const configError = err instanceof ConfigError ? err : new ConfigError((err as Error).message);
-      console.error(`[config] ${configError.message}`);
+      log.error("config reload failed", { error: configError.message });
       for (const listener of this.errorListeners) listener(configError);
     }
   }